docs: def export(self, nidm_version, export_dir):
          """
          Create prov entities and activities.
          """
          # We can not have this as a dictionnary because we want to keep the
          # duplicate prov:type attribute
          atts = (  # (PROV['type'],PROV['Location']),
              (PROV['type'], NIDM_COORDINATE),
              (PROV['type'], PROV['Location']),
              (PROV['label'], self.label)
              )
  
          if self.coord_vector is not None:
              atts = atts +\
                  ((NIDM_COORDINATE_VECTOR_IN_VOXELS,
                    json.dumps(self.coord_vector)),)
  
          # FSL unnormalised subject-level analyses do not provide coordinates in
          # voxels
          if self.coord_vector_std is not None:
              atts = atts +\
                  ((NIDM_COORDINATE_VECTOR, json.dumps(self.coord_vector_std)),)
  
          self.add_attributes(atts)